THE COOKING OF VEGETABLE FOODS.—=Bread= is either vesiculated or unvesiculated; the latter being what is called unleavened bread. Vesiculation of bread has usually been produced by _fermentation_ of some of the sugar of the flour. The starch first becomes sugar (dextrose) and then the growth of the yeast plant in the dough splits this up into alcohol and carbonic acid gas. The carbonic acid percolates the substance of the dough, rendering it porous. When it has “risen” sufficiently, the dough is placed in the oven. The heat of the latter kills the yeast plant, thus preventing any further fermentation, but at the same time expands the carbonic acid gas in the bread, rendering the latter still more porous, and drives off in a gaseous condition the greater part of the alcohol produced by the previous fermentation. It is objected to this plan of making bread, that a little of the sugar is wasted in producing alcohol and carbonic acid. To remedy this, _another plan_ is sometimes adopted, as first proposed by _Dr. Dauglish_. In it the dough is charged with carbonic acid dissolved in water under considerable pressure. The gas escapes in the substance of the dough, and on baking expands as in the ordinary method of making bread. Bread made in this manner, is called “aerated bread.” Nevill’s bread has a solution of carbonate of ammonia incorporated in the dough, which is dissipated by heat, thus causing vesiculation of the bread. On the continent, a mixture of hydrochloric acid and carbonate of soda is commonly used, carbonic acid and common salt being formed in the dough. Thus NaHCO₃ + HCl = NaCl + H₂O + CO₂. The hydrochloric acid employed should be perfectly pure and free from arsenic. Baking powders are also largely used for making cakes. “Self-raising” flour is flour with which baking-powder has already been mixed. Most baking-powders consist of a mixture of carbonate of soda and tartaric acid or bitartrate of potash, diluted with starch. When wetted, carbonic acid gas is evolved. A few contain alum, which is now an illegal material for this purpose. Ten pounds of flour ought to make thirteen to fourteen of bread. The use of stale bread is much more economical than of newly-made bread; besides this, it is more digestible. Newly-made bread is more palatable than stale, but it is more cohesive, and does not crumble into separate particles like stale bread. The consequence is, that it is less digestible, being less easily penetrated by the saliva and other digestive juices. The effect of _toasting_ is to render bread more friable, and consequently more digestible. It ought, however, to be thin and eaten soon after it is made; when thick and kept too long, it becomes tough and leathery. =Pastry= is less easily digested than ordinary bread. The lard or dripping added renders it more flaky and less easily pulverised; and, in addition, the fat coats over the starch cells; and thus the action of the digestive juices on the pastry is impeded.